i have a very bad gas mileage. My car is almost 16 mpg city, i dont know if im drive a shorts distance(6 miles sometimes) and most of the times are hills but dont high slopes.
I dont have any O2 codes, do i have to change the sensor after 130,000 miles?? my max is 95 gxe auto.
Sometimes my cel pull me 0302, 0304 like 1 time per month, but after 2 weeks not codes

What else do i have to check? i remplaced, plugs, tranny fluid, fuel filter, pcv, belts, clena TB, IAC, EGR.

 

16mpg city sounds normal to me. Especially for an automatic Maxima.

 

that's not very far off from what it should be. Depending on how you drive as well, it's not very bad. I think we're only supposed to get around 20-21 mpg city at the best of times.

Check your EGR components ... and clean your AICV...which I am about to do as soon as it's not 15 degrees.

 

Try pulling the codes even without a CEL.
0304 by itself will not light up a CEL.
Just realise also that in the cold season and with city driving, you should probably get 18-20mpg so you are not far off. Just keep checking the mpg for the next few tanks. Also, I hope you are using premium fuel and have NGK spark plugs.

 

also, have you every used fuel system cleaner? Your injectors could be dirty.

 

yes, i cleaned my injectors a few weeks ago, clean the IAC, EGR system, maybe is normal here where a live, theres a lot of hills and that S...t.